she won't be round forever anyway especially as she comes into her own. if you feel that she's in on it, if i were you, i'd just cut all ties.
children are very tolerant as long as they have a stable base(you and your family). he will get over it. money isn't everything unless you rely upon her while you are working. if it's just for entertainment, look elsewhere; it will give you peace of mind. why put up with crap if you don't really have to?